Reverb Time Calculator
Enter your session tempo and get pre-delay and decay times that fit the groove instead of blurring it. Click any value to copy it.
How to use it ↓Pre-delay, by note value
| Note Value | Pre-delay (ms) | Verdict |
|---|
Decay (RT60) that clears the next hit
| Tail fits inside | Window (ms) | Decay to set (ms) | In seconds |
|---|
Reverb is the effect most producers reach for first and the one most likely to ruin a mix. Not because it sounds bad on its own, but because it is the only effect whose output keeps sounding after the input has stopped. Set the tail slightly too long and every beat arrives on top of the last one, and the mix turns to soup without any single element sounding wrong.
The fix is not subtlety, it is arithmetic. If you know your tempo you can work out exactly how long a reverb is allowed to ring before the next hit lands, and set the decay to just under that. This page does that calculation, and the rest of this guide explains what the two numbers mean and how to choose between them.
The Only Two Controls That Matter
Reverb plugins ship with a dozen knobs. Two of them decide whether the reverb works.
Pre-delay is the gap between the dry sound and the first reflection, measured in milliseconds. In a real room it is the time sound takes to reach a wall and come back, so a big room has a longer one. In a mix it does something more useful: it keeps the reverb off the attack. With no pre-delay, the tail starts at the same instant as the word or the snare hit and smears it. With twenty or thirty milliseconds, the attack lands dry and clear and the reverb arrives just behind it.
Decay, often labeled time or RT60, is how long the tail takes to fall by 60 decibels, which is effectively to silence. This is the number that decides whether your reverb is a room, a hall or a mistake. It is also the one people set by feel, on a solo track, where a long tail always sounds lovely and always turns out to be too long in the mix.
Why Tempo Is the Right Unit
Pick a reverb tail at random and it will end somewhere arbitrary: three quarters of the way through a beat, or a little past the next one. Your ear does not hear that as a natural room, it hears it as a smear that never quite lines up.
Lock the tail to the grid instead and the reverb becomes rhythmic. If it has faded by the time the next snare lands, every snare gets a clean attack and the space between them is full. If it has faded by the end of the bar, the track breathes once per bar, which is the sound of most well-produced pop records.
The arithmetic is the same as for delay. One beat in milliseconds is 60,000 divided by the tempo. At 120 BPM that is 500 ms per beat, so a bar of 4/4 is 2,000 ms. The calculator above takes those windows and subtracts your chosen pre-delay, because pre-delay and decay are consecutive, not simultaneous: the tail cannot start until the first reflection has.
Set the decay by ear while the whole mix plays, never soloed. Reverb that sounds perfect on a solo vocal is almost always twice as long as the mix can carry, and this is the single most common reverb mistake there is.
Pre-Delay: the Useful Range
Pre-delay is only doing its job inside a fairly narrow window, and the calculator flags this in its verdict column.
- Under about 10 ms is too short to separate anything. The reverb still lands on the attack, which is the problem you were trying to solve.
- Roughly 10 to 50 ms is the working range. The attack stays dry, the reverb sits behind it, and nobody hears a separate event.
- Between 50 and 100 ms still works on slow, sparse material, where there is room for the gap. On anything busy it starts to drag.
- Past about 100 ms the first reflection is heard as its own event. That can be deliberate, the slapback that sits between reverb and delay, but it is not transparent any more.
Because the useful window is fixed in milliseconds and note values are not, the right subdivision changes with tempo. A sixteenth note at 90 BPM is 167 ms, which is a distinct echo rather than a pre-delay. The same sixteenth at 170 BPM is 88 ms, long but usable. The sixty-fourth note is the one that lands in range at almost any tempo, which is why the calculator defaults to it, lists the rest, and tells you which are usable rather than leaving you to guess.
Choosing a Decay Window
Four windows cover almost everything, and the calculator gives all four.
| Window | What it does | Use it on |
|---|---|---|
| One beat | Tail is gone before the next beat lands | Drums, percussion, dense arrangements, anything fast |
| Two beats | Half a bar of space | Rhythm guitars, keys, backing vocals |
| One bar | Breathes once per bar | Lead vocals, the default starting point |
| Two bars | Washes across the phrase | Pads, ambient, sparse arrangements, the last chord |
Start at one bar for a lead vocal and one beat for a snare, then shorten. Almost every reverb problem is fixed by making the tail shorter, and almost none by making it longer.
Fitting Reverb Into a Busy Mix
Three moves, in the order worth trying them.
High-pass the reverb return. Low frequencies carry the most energy and the least information about space, so a reverb allowed to ring below 200 Hz stacks up bass with every hit. Cutting the return around 200 to 300 Hz loses nothing you wanted and clears out most of the mud. Our low end guide covers why this matters more than any other single cut.
Shorten the decay before you lower the level. Turning a too-long reverb down makes it quieter and just as smeared. Shortening it fixes the actual problem and usually lets you keep more of it.
Use one reverb, on a send. Several different reverbs on several tracks put the instruments in several different rooms, which is exactly the incoherence you are trying to avoid. One send, fed at different amounts, puts everything in one place.
Frequently Asked Questions
What is reverb pre-delay?
The gap between the dry sound and the first reflection of the reverb. It keeps the tail off the attack, so a vocal stays intelligible and a snare keeps its crack. Ten to forty milliseconds covers most sources.
How do I set reverb decay to the tempo?
Pick the window you want the tail to live inside, usually one beat for a tight mix or one bar for a big one, then set the decay so the reverb has faded by the end of it. The calculator above works both out from your BPM and subtracts the pre-delay, so the whole tail fits.
What is RT60?
The time a reverb takes to fall by 60 decibels, which is effectively to silence. It is what the decay or time control on a reverb plugin is setting, and it is the number you match to a beat or a bar.
Should pre-delay be tempo synced?
It helps and it costs nothing, because it puts the first reflection on a subdivision the track already contains. Watch the actual milliseconds though: past about fifty the pre-delay is heard as a slap echo rather than as part of the reverb.
Why does my reverb make the mix muddy?
Usually the tail is still sounding when the next hit arrives, so every beat layers on the last. Shorten the decay until it clears the next beat, add pre-delay to get the attack back, and high-pass the reverb return so its low end stops stacking up.
Where to Go Next
The companion to this page is the delay time calculator, which does the same job for echoes, and the two are worth having open together: a delay and a reverb fighting over the same rhythmic space is the other classic way to lose a mix. For the musical side of reverb, what each type is actually for and when to reach for a plate over a hall, read how to use reverb. If you are not sure of your track's tempo to begin with, the BPM calculator will get you there.